The important parts within those desktop service file are the referenced X-KDE-Library which will be loaded on request and is responsible for executing our with X-KDE-PluginKeyword defined Ruby scrip file. Our applet will be known by Plasma under the unique name "plasma-ruby-web-applet".

The Ruby Script

It follows the Ruby scripting code which does implement the whole functionality to display a webbrowser within the applet and to browse around using the displayed links.

# On initialization this method will be called by plasma. Here we
# are able to do expensive initialization work to show something
# within our applet.
def init
# Let's start with a nice default size.
resize(600, 400)

# This method will be called once the user clicks on a link.
# We just load the defined URL-address and let the
# webbrowser-page display the content.
def load(url)
puts "Loading #{url.toString}"
@page.url = url
end

# This method will be called once loading a page finished.
def loadFinished(success)
puts "page loaded #{@page.page.currentFrame.url.toString}"
end

# This method will be called each time a constraint changed. the
# for us most interesting constraints are;
# * LocationConstraint if the location of the applet changed
# * ScreenConstraint if the screen on which the applet is located
# on changed
# * SizeConstraint if the size of the applet changed
# * ImmutableConstraint if the applet got locked/unlocked
def constraintsEvent(constraints)
if constraints.to_i & Plasma::SizeConstraint.to_i
# if the size of the Applet changed, then resize also the
# webbrowser.
@page.resize(size())
end
end

end

end

That was already all the code needed to implement our own webbrowser Applet using the Ruby language. The in this sample used webbrowser does provide additional functionality to use optional a full powered webbrowser or adopt it to your needings.

Install and test the Applet

To install the Applet the CMakeLists.txt is used. It basically does copy the both files above to the right locations. Translated to command-line arguments it would look like;

what installs the both files to the global installation directory to make hem available for all users on your sysem. If you like to have them accessible only from within one user, then just copy those both files to the users $KDEHOME (the command "kde4-config --localprefix" should provide you a hint where that may be).

To take a look at your applet or test it during development, you can;

kbuildsycoca4
plasmoidviewer plasma-ruby-web-applet

where the kbuildsycoca4 does rebuild the desktop-cache to update changes done to the desktop file. The plasmoidviewer is a tool that allows you to start and view your applet outside of plasma.